The TARDIS brings the Doctor, Amy and Rory to the tiny Welsh village of
Cwmtaff in the year 2020. There, a drilling project seeks to burrow deep
beneath the surface of the Earth. Strange craters have begun opening up
near the drill site, however, dragging people into the ground -- and Amy
becomes the latest victim. Investigating, the Doctor realises that the
drill has awakened a tribe of Silurians from their aeons-long slumber.
Believing themselves to be under attack, the Silurians are now on a war
footing, preparing an offensive against the human race.

Production

By late 2008, Chris Chibnall had largely left Doctor Who behind
him. His lone script for the series, 42,
had aired as part of Season Twenty-Nine, and he had recently stepped down
as co-producer and head writer of Torchwood following its second
season. In October, then, he was surprised to find himself contacted by
Steven Moffat, the new executive producer of Doctor Who. Moffat had
liked Chibnall's latter Torchwood scripts -- such as Adrift, Fragments and Exit Wounds -- and wanted to
recruit him for Season Thirty-One. In particular, Moffat knew that he
was a lifelong, diehard Doctor Who fan, and so he had earmarked
Chibnall for a special project.

Since its return in 2005, Doctor Who had gradually been
reintroducing the most memorable villains and monsters of the classic era.
To date, these had included the Daleks, the Cybermen, the Master, the
Sontarans, and most recently Davros. For Season Thirty-One, Moffat wanted
to bring back the Silurians, a race of lizard people who had been Earth's
original dominant species until an anticipated disaster sent them into
aeons of hibernation deep beneath the surface. The Silurians had been
created by Malcolm Hulke for 1970's The
Silurians in which they encountered Jon Pertwee's Third Doctor,
and the writer had also given them aquatic cousins in The Sea Devils two years later. Both species
of homo reptilia had then appeared in 1984's Warriors Of The Deep.

Steven Moffat felt that the original Silurians' third eye
was now associated with Davros

Although the appearance of the Silurians had been broadly consistent
between their two previous serials, Moffat encouraged Chibnall to devise
a new branch of the race for their twenty-first century revival. In
particular, Moffat wanted to dispense with the Silurians' third eye,
which he felt was now associated with Davros. In its place, Chibnall
conceived the whiplike tongue with which the new Silurians could poison
their enemies.

Chibnall was given a two-part slot for Season Thirty-One, and began
writing episodes entitled “The Ground Beneath Their Feet” and
Cold Blood. In addition to the earlier Silurian stories, the writer
echoed classic imagery from the Pertwee era: the Discovery Drilling
Project was reminiscent of the eponymous experiment in Season Seven's Inferno while the force field the Silurians
created around Cwmtaff was much like the heat shield around Devil's End in
the Season Eight finale The Daemons.
Chibnall also suggested that the Silurian guns could bear a marked
resemblance to those wielded by the Sea Devils. Two of the Silurian
names were corruptions of Doctor Who personnel who had worked
during the Pertwee years: Malohkeh for Malcolm Hulke and Restac for
script editor Terrance Dicks.

One major story element that was ultimately excised from Chibnall's
scripts was a new monster called the Armasaurs, armadillo-like dinosaurs
which would emerge from the Silurians' shafts to abduct people. It soon
became clear that the budget for the episodes would not permit both the
Armasaurs and the sophisticated prosthetics necessary for the Silurians.
Thus the Armasaurs were replaced by the bioprogrammed quicksand, and
Alaya was introduced earlier in “The Ground Beneath Their
Feet” to provide a mobile, sentient threat.

The Silurian story would be made as the fourth recording block for Season
Thirty-One under director Ashley Way. Way was a newcomer to Doctor
Who proper, but his work on the interactive episode Attack Of The
Graske and the downloadable TARDISode prequels for Season
Twenty-Eight had led to no fewer than six credits on Torchwood,
including Captain Jack
Harkness, Kiss Kiss, Bang
Bang and Exit Wounds.
Away from the world of Doctor Who, Way had also directed episodes
of Casualty, Belonging and Crash.

Arthur Darvill was uncertain whether or not this was truly
the end of Rory

The production of “The Ground Beneath Their Feet” and Cold
Blood began in October 2009. Ironically, although Rory's death at the
story's climax was a major turning point for the entire season, Arthur
Darvill had played the character only once before, in the just-completed
The Eleventh Hour. Darvill knew that he
would be filming two additional episodes -- The
Vampires Of Venice and Amy's
Choice -- which would air prior to the Silurian story, but at this
point he was uncertain whether or not this was truly the end of Rory.

The first five days of filming, from October 20th to 24th, took place in
and around St Gwynno's Church in the Welsh hamlet of Llanwonno, including
the adjacent cemetery. The area around the Northover residence was
actually Bedwellty Pitts in Tredegar; Way's team was there on October
26th. The next day, Tower Colliery in Hirwaun provided the exterior of the
Discovery Drilling Project, as well as the control room. However, scenes
in the storeroom from which Mo and Amy were abducted were recorded at
Mir Steel in Newport from the 28th to the 30th; material in the drill site
corridors was also taped on the 30th.

November saw cast and crew travel to Hensol Castle in Hensol, where
sequences in the church crypt were filmed on the 2nd and 3rd. Clips of Amy
and Rory enjoying each other's company were also captured on the second
day, to form part of Amy's vain attempt to remember Rory after he is
erased from time. November 4th to 7th saw the first studio scenes recorded
for “The Ground Beneath Their Feet” / Cold Blood at
Upper Boat Studios; these chiefly took place in areas of the Silurian
city, although the TARDIS set was in use on the 6th. Then it was back
out on location from the 9th to the 12th, with the Temple of Peace in
Cardiff dressed as the Senate chambers. Some elements of Rory's death
were also recorded there, and this work continued back at Upper Boat on
the 12th, when further TARDIS material was also completed.

Dropped in editing was a conversation about faith which
foreshadowed Rory's fate

More scenes in the Silurian city were filmed on November 13th at the
Plantasia botanical gardens. This work continued at Upper Boat from the
16th to the 18th -- particularly for those sequences in Malohkeh's
laboratory. Various insert shots were also completed at this time. While
this marked the end of principal photography on “The Ground Beneath
Their Feet” / Cold Blood, a foot-angle perspective of the
Doctor jumping up and down in the graveyard was taped at Upper Boat on
January 13th, 2010, and long shots of Mo on his bicycle were captured at
The Vicarage in Rhymney on January 29th.

Both The Hungry Earth -- as the first episode was renamed -- and
Cold Blood badly overran, even despite the latter being granted a
fifty-minute timeslot as opposed to the usual forty-five. As a result, Way
found himself cutting a number of important elements from both episodes.
In The Hungry Earth, much was originally made of the fact that the
Discovery Drilling Project was under pressure from its financial backers
to reach greater depths more quickly -- a plot strand to which Meera
Syal, who played Nasreen, made reference in some of her media interviews
for the serial. Cold Blood lost Amy and Mo's discovery that the
Silurians have kidnapped a menagerie of modern animals, including a dog
owned years earlier by Tony Mack. Also dropped in editing was an
extensive conversation about faith between Rory and Alaya, which would
have foreshadowed Rory's fate at the end of the story.